Louis van Gaal has warned Manchester United they still have much work to do before they secure Champions League qualification.

United returned to winning ways on Saturday with a 3-1 victory over Leicester at Old Trafford.

Robin van Persie put United ahead with a sublime finish and Radamel Falcao added his fourth for the club before Wes Morgan's own goal helped United avenge their embarrassing 5-3 reverse at the King Power Stadium last September.

Louis van Gaal expects more improvement from his team after Manchester United beat Leicester City 3-1

Robin van Persie (second left) celebrates his goal for United against Leicester

The win lifted Van Gaal's team to within five points of second-place Manchester City and also went some way to appeasing the fans who watched their team play out an uninspiring 0-0 draw at Cambridge last week.

But Van Gaal reminded his players following the win that the season is far from over.

'No, because (only) at the end of the league matches we divide the titles and not at this moment,' the United boss said when asked if he could sense Champions League qualification was getting closer for his men.

United have a winnable set of fixtures coming up against West Ham, Burnley, Swansea, Sunderland and Newcastle.

But Van Gaal is aware he still has to travel to Liverpool and Chelsea in the last third of the season and he believes the fight for a top-four finish will go right down to the wire.

'It shall be a big battle to the end,' Van Gaal told MUTV.

'That is a big battle. West Ham has lost (to Liverpool on Saturday).

'One competitor shall lose.'

Radamel Falcao celebrates scoring his fourth goal for the club against Leicester on Saturday

Van Gaal (right) shakes hands with Leicester's Esteban Cambiasso (left) after the game at Old Trafford

Van Persie candidly admitted on Monday that he had under-performed this season.

But he looked like his old self for long periods on Saturday and his goal was out of the top drawer.

Van Persie watched Daley Blind's pass float over his left shoulder before he stabbed the ball past Mark Schwarzer first time with his right boot.

Replays showed the striker was lucky the goal was allowed to stand, though, as he was marginally offside.

Van Gaal felt for his opposite number Nigel Pearson, and admitted such errors will only be stopped if more technology is introduced into the game.

'I think also it was offside but it always happens in games that the referee or a linesman are not in a good shape at that moment but you cannot avoid that,' Van Gaal said.

'You need modern techniques always and when you don't use them in this modern time it shall happen every game.'

While United have City in their sights, it is a completely different story for Leicester, who remain rooted to the foot of the Barclays Premier League.

Van Persie's (right) goal was spectacular but there were suspicions of offside

Ritchie De Laet (left) is hopeful that Leicester will still be able to avoid relegation from the Premier League

The Foxes are three points from safety but defender Ritchie De Laet is still confident his team will not be relegated.

'The United game was a bonus game, no one was expecting us to take anything from it,' said De Laet, who left United for Leicester three years ago.

'But our confidence is still high.

'I think we can get out of it. You just have to look at the last five performances. We have had three wins out of them so we know we can give teams a good game.